The microprocessor control units (MCUs) are dominantly adopted as main controlling units in the most electronic products currently so that specific product functions are achieved by mere adjustments of the firmware of the MCU for the expected commercialization.
Taking the cheapest common MCUs into account, they usually bear insufficient input/output pins, whereby there are no exclusive serial communication interfaces supported thereby generally, such as IIC, SPI and UART commonly used for the MCUs. Chances are that there would be more than one MCU and other devices having serial communication interfaces included in a product, such as a memory unit, an LCD driver and an AD converter, to operate with one another for the functions of the product. For the mutual data transmission among these devices, it would be necessary that the general purpose input/output pins of the MCU are electrically connected to the serial communication interfaces of the other devices, wherein the operation process therefor would be written into the firmware of the MCU to simulate the aforesaid standard serial communication interface for the mutual data transmission.
Since the standard serial communication interface is simulated by the firmware, there would be a frequent necessity for real-time services by the MCU to satisfy the requests of communication timing. However, the whole performances of the MCU are always selectively lowered if the communication process and other tasks shall be executed simultaneously when the firmware of the MCU is heavily loaded in real time in a certain occasion. For example, when a task for playing voices is executed by a cheap MCU, the satisfactions for the sampling rate for playing voices would be considered firstly, but when there are necessary external communications to be additionally maintained at the same time, the real time service requests for the above two tasks would be hardly met by the MCU. Generally, there are several limitations to the communication timing and if the requests thereof fail to be met, the data transmissions will fail. On the other hand, when the MCU is heavily loaded to satisfy the two tasks needing real time services at the same time, the priority arrangements for the tasks would be difficult. The quality in voice playing would be sacrificed when the sampling rate therefor is lowered or not executed by original sampling rate for the sake of the real time serial communication requests. Oppositely, there would be errors in communication tasks when the quality for voice playing is necessarily met and the real time requests for serial communications fail to be met correspondingly. Accordingly, the whole functional performance of the MCU is limited.
For breaking the strict limit to the transmission timing of communication tasks, the research and development engineers often design specific serial handshaking transmission communication methods achievable by the MCU firmware with 3 or more than 3 signal lines, wherein there is often an additional busy signal line exclusive for handshaking controlling besides the data signal line and the clock signal line for the serial transmission by 3 lines. Though the strict limit to the transmission timing of communication tasks is broken by the above common method through handshaking controlling protocol, there exist defects thereof as follows: 1. the cost for product fabrication would be increased for expanding the input/output pins by additional circuits for the low priced MCU with insufficient input/output pins when 3 or more than 3 general purpose input/output pins are necessary for the hardware resources of the MCU; 2. there would be low transmission efficiency owing to more inversions for the handshaking controlling states.
Accordingly, to necessarily compensate for the decreased efficiency in the common scheme as abovementioned, there would be a criterion to comply with the requirements that low amount of firmware resources are consumed, there are less input/output pins necessary for the communication transmissions and there is no strict timing limit, when applying the firmware in the low-priced MCU to the serial communication interface. As a result, the present invention is developed for the purpose of improving the above common defects in this art.
In order to overcome the drawbacks in the prior art, a two-wire serial handshaking communication interface and a method thereof is provided. The particular design in the present invention not only solves the problems described above, but also is easy to be implemented. Thus, the invention has the utility for the industry.